Abstract

We analyzed a kinematic earthquake rupture generator that combines the randomized spatial field approach of Graves and Pitarka (Bull Seismol Soc Am 106:2136–2153, 2016) (GP2016) with the multiple asperity characterization approach of Irikura and Miyake (Pure Appl Geophys 168:85–104, 2011) (IM2011, also known as Irikura recipe). The rupture generator uses a multi-scale hybrid approach that incorporates distinct features of both original approaches, such as small-scale stochastic rupture variability and depth-dependent scaling of rupture speed and slip rate, inherited from GP2016, and specification of discrete high slip rupture patches, inherited from IM2011. The performance of the proposed method is examined in simulations of broadband ground motion from the 2016 Kumamoto, Japan earthquake, as well as comparisons with ground motion prediction equations (GMPEs). We generated rupture models with multi-scale heterogeneity, including a hybrid one in which the slip is a combination of high- slip patches and stochastic small scale variations. We find that the ground motions simulated with these rupture models match the general characteristics of the recorded near-fault motion equally well, over a broad frequency range (0–10 Hz). Additionally, the simulated ground motion is in good agreement with the predictions from Ground Motion Prediction Equations (GMPEs). Nonetheless, due to sensitivity of the ground motion to the local fault rupture characteristics, the performance among the models at near-fault sites is slightly different, with the hybrid model producing a somewhat better fit to the recorded ground velocity waveforms. Sensitivity tests of simulated near-fault ground motion to variations in the prescribed kinematic rupture parameters show that average rupture speeds higher than the default value in GP2016 (average rupture speed = 80% of local shear wave speed), as well as slip rate durations shorter than the default value in GP2016 (rise time coefficient = 1.6), generate ground motions that are higher than the recorded ones at periods longer than 1 s. We found that these two parameters also affect the along strike and updip rupture directivity effects, as illustrated in comparisons with the Kumamoto observations.

Highlights

  • The characterization of earthquake rupture has been at the forefront of new developments in numerical methods for strong ground motion simulations of crustal and subduction zone earthquakes

  • We propose a kinematic earthquake rupture generator that combines the approach of Graves and Pitarka (GP2016) (Graves and Pitarka 2016) with the multiple asperity rupture characterization approach of Irikura and Miyake (IM2011) (Irikura and Miyake 2011)

  • In order to be consistent with the GP2016 model, the rupture speed for IMh1 is set at 80% of the local shear wave velocity, which is slightly higher than the value of 72% prescribed by the recipe

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Summary

Introduction

The characterization of earthquake rupture has been at the forefront of new developments in numerical methods for strong ground motion simulations of crustal and subduction zone earthquakes. The longperiod energy radiated from the shallow rupture largely affected the near-fault permanent slip, and the high-slip rate area might have generated high frequency ground motion that was observed in the heavy damage zone (Kawase et al 2017) These features are similar to rupture characteristics observed during recent large subduction zone earthquakes Because large crustal earthquakes break the entire seismogenic zone, the rupture and, the radiated seismic energy is affected by depth-dependent variations of stress and frictional properties in the upper crust This can explain the observed spatial separation between low-frequency and high-frequency generation areas, and variations of rupture kinematics with depth for large earthquakes. We show results from sensitivity tests of simulated near-fault ground motion to variations in the prescribed kinematic rupture parameters, such as rupture speed, slip duration rate, and slip contrast between the large slip areas and background slip

Kinematic Rupture Models
Rupture Models
Ground Motion Modelling
30 KMMH01 0
Sensitivity of Ground Motions to Rupture Parameters in HB2 Model
Findings
Conclusions
Full Text
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